STUDIES OF STREPTOMYCES-RETICULI CEL-1 (CELLULASE) GENE-EXPRESSION INSTREPTOMYCES STRAINS, ESCHERICHIA-COLI, AND BACILLUS-SUBTILIS

Various Streptomyces strains [Streptomyces lividans 66, Streptomyces v inaceus, and Streptomyees coelicolor A3 (2)] acquired the ability to u tilize crystalline cellulose (Avicel) after transformation with a mult icopy vector containing the cel-1 gene from Streptomyces reticuli. The expression level in these hosts was two to three times lower than in S. reticuli, indicating the absence of positive regulatory elements. L ike S. reticuli, they processed the Avicelase to its catalytic domain and to an enzymatically inactive part. The cel-1 gene with its origina l upstream region was not expressed within Escherichia coli. When cel- 1 had been fused in phase with the lacZ gene, large quantities of the fusion protein were produced in E. coli. However, this protein was enz ymatically inactive and proteolytically degraded to a series of trunca ted forms. As the cellulase (Avicelase) synthesized by S. reticuli is not cleaved by the E. coli proteases, its posttranslational modificati on is proposed. With Bacillus subtilis as host, the cel-1 gene was exp ressed neither under its own promoter nor under the control of a stron g Bacillus promoter.